It will not be surprising to tell you that some people in the world, unfortunately, do not believe in the findings of traditional reputable science and put excessive stock in pseudoscience. There are many different reasons for this phenomenon[1][2]. Even among those of us who have not succumbed to such false beliefs, a ready defense for these pseudoscience believers is sometimes made. It may be presented by saying “it isn’t causing any harm for them to believe in that”. To be a rational skeptic such defenses cannot be taken without further investigation. When it comes to belief in pseudoscience there can in fact be drastic consequences. A perfect example of the dangers of pseudoscience is the belief that vaccines cause autism. By assessing the claims, facts, and outcomes of this pseudoscientific belief the rational skeptic may see the risks involved in accommodating such untrue claims.

To begin it must be made clear what I mean when I say science and when I say pseudoscience. By science I mean what scientists do; they investigate an event in the nature to contribute to our overall understanding of the natural world. This is compared to pseudoscience, which involves making claims or presenting “findings” (typically supported with logical flaws) that do not contribute to the understanding of the world[3]. The claim that vaccines cause autism fits these criteria because all sound, valid studies with good research methodology and design have shown that there is no link between vaccines and an autism diagnosis. In contrast, all support for this link has been presented through unsound reasoning, invalid conclusions, or poor research design and methodology. In many cases testimonials that a person’s child was vaccinated before he was diagnosed with autism is the only evidence. None of these flawed forms of evidence have contributed to the larger understanding of world. In fact, these sources are far outnumbered by the better quality studies conducted, again showing little reason to trust in their claims. It may not be impossible, but it is so improbable that it might as well be.

What are the claims of the anti-vaccination camp in relation to autism? In general they claim that vaccines are toxic, do not increase immunity, and that they cause autism and other developmental disabilities[4][5][6][7][8]. With autism this was really started when Andrew Wakefield and colleagues published an article in the medical journal the Lancet claiming a link between autism and the mumps, measles, and rubella (MMR) vaccine[9]. In 2010 this article was retracted by the Lancet when its medical panel concluded that “Dr. Wakefield had been dishonest, violated basic research ethics rules and showed a ‘callous disregard’ for the suffering of children involved in his research”[10]. That same year Wakefield had his medical license revoked for unethical practice relating to this study[11]. To elaborate, he took a biased sample of participants without informed consent (from his son’s birthday party) and he did not disclose that the study was partly funded by a lawyer for a family seeking to sue vaccine makers[12]. This may be why his study came the conclusions it did, but was never corroborated by any other study conducted with good methodology.

Despite the former Dr. Wakefield’s unethical and unscientific practices coming to light, as well as his clear bias of financial gain, many who believe his uncorroborated claims will not be convinced. Some have noted that the actions taken to discredit Wakefield will be seen by devotees of the anti-vaccine movement as proof of the “conspiracy” propagated by the government and the scientific community[13], which is unlikely[14]. A large number of parents whose child has a diagnosis of autism still believe vaccines are the cause[15], which is less surprising with the voice of celebrities on the side of the anti-vaccine movement[16][17][18]. This is in the face of a multitude of studies discrediting this claim[19][20][21][22][23][24].

For all those parents who are not convinced that vaccines do not cause autism it makes some sense, as there is a rising in the diagnosis of autism[25][26].A brief walk through some of the evidence involving autism prevalence and vaccines may illuminate possible reasons for the rise in autism diagnoses and help clarify why vaccines are not likely the cause. To begin with the effects of the MMR vaccine on autism diagnoses a study by Uchiyama and colleagues investigates the cases of autism diagnoses before, during and after use of the combination MMR vaccine at a clinic in Japan[27]. They compared the before, during and after groups of patients, as well as those who opted out of the MMR during the MMR period. The researchers found no link between autism diagnosis and MMR vaccination.

Next, a look at other reasons for rising autism diagnoses. Researchers Tidmarsh and Volkmar note that the criteria changes in the DSM-III- TR[28] and the DSM-IV[29] were overly inclusive[30]. The changes in autism diagnosis criteria in the DSM-V are expected to decrease the prevalence of autism[31], suggesting that at least part of the increase was due to overly inclusive diagnostic criteria. Tidmarsh and Volkmar also overviewed the changes in assessment tools, reporting methods, and general knowledge of autism spectrum disorders, which would all possibly increase the prevalence of autism. Catherine Maurice in her book Let Me Hear Your Voice[32], about her families struggle with autism, suggests that many professionals she encountered were less than knowledgeable about autism. Croen and colleagues overviewed prevalence in California in individuals serviced by the Department of Developmental Services and found that part of the increase in prevalence was due to a reclassification of children as autistic who had previously obtained the diagnosis of mental retardation[33] unknown cause[34].

Now it may seem clearer why there is no link for the increase in autism prevalence, as well as why there would be an increase in the first place; but some people may still say “what is the harm”. The harm is what happens when people believe vaccines cause autism. Namely, they do not vaccinate their children[35]. This is the reason for the rising cases of measles, mumps, and rubella[36], which has resulted in scores of unnecessary illness and even many deaths[37]. A common objection by doubters is that the likelihood of getting autism is higher than death from measles, but that was not always true. Before advances in medical science the rates of death from measles was nearly double that of getting autism[38][39]. All in all, “the harm” is people’s health and lives.

To be a rational skeptic it is important to look at the logical end of any action or claim. The logical end of anti-vaccine beliefs is the increased probability of harm to human lives over time. Pseudoscience and junk science can cause dangerous decisions to be made. For this reason it is very important to investigate with rational skepticism all ideas that affect our actions. Those in the anti-vaccine movement have used an irrational skepticism to defame probable sources of valid and sound information. We must be cautious of this type of thinking or it may lead to perilous actions that don’t make sense.